1. Field of the Invention
This invention relates to a differential pressure measuring transducer assembly using a measuring diaphragm of semiconductor material for measuring a differential pressure between two fluids by converting the differential pressure into a strain and detecting the strain as a variation or change in electrical resistance.
2. Description of the Prior Art
In one type of measuring diaphragm of semiconductor material, such as silicon, for measuring a differential pressure, the diaphragm having a center area and a peripheral area of large thickness and an intermediate area of small thickness as disclosed in U.S. Pat. No. 4,364,276, for example, includes a strain producing portion disposed in the small thickness intermediate area in which a gauge resistance is provided by a dispersion method or an ion implantation method. This type of measuring diaphragm offers the advantage that substantially the same characteristics can be obtained even if the pressure is applied in different directions (whether the pressure is applied on the gauge surface or on the opposite side).
However, this type of measuring diaphragm suffers the disadvantage that the linearity of the pressure and output deteriorates when the pressure differential between a fluid under high pressure and a fluid under low pressure being measured is very small. This phenomenon is accounted for by the fact that, although it is necessary to further reduce the thickness of the small thickness area of the measuring diaphragm to effectively carry out measurements in the low pressure differential range, a reduction in thickness produces a deflection in the small thickness area, resulting in the production of what is usually referred to as a balloon effect in the measuring diagram in which the central area thereof expands.